Sangeeta Ray Banerjee

Comprehensive Radiolabeling, Stability, and Tissue Distribution Studies of Technetium-99m Single Amino Acid Chelates (SAAC)

Technetium tricarbonyl chemistry has been a subject of interest in radiopharmaceutical development over the past decade. Despite the extensive work done on developing chelates for Tc(I), a rigorous investigation of the impact of changing donor groups and labeling conditions on radiochemical yields and/or distribution has been lacking. This information is crucially important if these platforms are going to be used to develop molecular imaging probes. Previous studies on the coordination chemistry of the {M(CO)(3)}(+) core have established alkylamine, aromatic nitrogen heterocycles, and carboxylate donors as effective chelating ligands. These observations led to the design of tridentate ligands derived from the amino acid lysine. Such amino acid analogues provide a tridentate donor set for chelation to the metal and an amino acid functionality for conjugation to biomolecules. We recently developed a family of single amino acid chelates (SAAC) that serve this function and can be readily incorporated into peptides via solid-phase synthesis techniques. As part of these continuing studies, we report here on the radiolabeling with technetium-99m ((99m)Tc) and stability of a series of SAAC analogues of lysine. The complexes studied include cationic, neutral, and anionic complexes. The results of tissue distribution studies with these novel complexes in normal rats demonstrate a range of distribution in kidney, liver, and intestines.

Heterobivalent agents targeting PSMA and integrin-αvβ3.

Differential expression of surface proteins on normal vs malignant cells provides the rationale for the development of receptor-, antigen-, and transporter-based, cancer-selective imaging and therapeutic agents. However, tumors are heterogeneous, and do not always express what can be considered reliable, tumor-selective markers. That suggests development of more flexible targeting platforms that incorporate multiple moieties enabling concurrent targeting to a variety of putative markers. We report the synthesis, biochemical, in vitro, and preliminary in vivo evaluation of a new heterobivalent (HtBv) imaging agent targeting both the prostate-specific membrane antigen (PSMA) and integrin-αvβ3 surface markers, each of which can be overexpressed in certain tumor epithelium and/or neovasculature. The HtBv agent was functionalized with either 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or the commercially available IRDye800CW. DOTA-conjugated HtBv probe 9 bound to PSMA or αvβ3 with affinities similar to those of monovalent (Mnv) compounds designed to bind to their targets independently. In situ energy minimization experiments support a model describing the conformations adapted by 9 that enable it to bind both targets. IRDye800-conjugated HtBv probe 10 demonstrated target-specific binding to either PSMA or integrin-αvβ3 overexpressing xenografts. HtBv agents 9 and 10 may enable dual-targeted imaging of malignant cells and tissues in an effort to address heterogeneity that confounds many cancer-targeted imaging agents.

Rhenium tricarbonyl core complexes with ligands derived from arylpiperazines. The structures of [Re(CO)3{NC5H4CH2N(H)CH2CH2–Fphenpip}]Br, [Re(CO)3{(NC5H4CH2)2N(CH2)3–CH3OphenpipH}]Br2 and [Re(CO)3{(CH3N2C3H2CH2)(O2CCH2)N(CH2)3–CH3OphenpipH2}]BrCl

Abstract The reactions of potentially tridentate ligands, derived from N-arylpiperazines, with [NEt4]2[Re(CO)3Br3] have been investigated. The compounds [Re(CO)3{NC5H4CH2N(H) CH2CH2–Fphenpip}]Br (1Br), [Re(CO)3{(NC5H4CH2)2NCH2CH2CH2–CH3OphenpipH}]Br2xa0·xa02CH2Cl2xa0·xa0H2O (2Br2xa0·xa02CH2Cl2xa0·xa0H2O) and [Re(CO)3{(CH3N2C3H2CH2)(O2CCH2)N(CH2)3–CH3OphenpipH2}]BrClxa0·xa01.5MeOHxa0·xa0H2O (3BrClxa0·xa01.5MeOHxa0·xa0H2O) have been prepared and structurally characterized. The compounds exhibit fac-[Re(CO)3N3] or fac-[Re(CO)3N2O] coordination geometry in the cationic molecular units. Both compounds are chemically robust and survive histidine and cysteine challenges with greater than 95% recovery. Crystal data for C21H23BrFN4O3Re (1Br): monoclinic P21/c, a=11.344(1) A, b=14.433(1) A, c=13.730(1) A, β=103.092(2)°, V=2189.5(2) A3, Z=4; C31H41Br2Cl4N5O5Re (2Br2xa0·xa02CH2Cl2xa0·xa0H2O): monoclinic P21/c, a=30.015(1) A, b=8.9324(4) A, c=14.7361(6)A, β=103.195(1)°, V=3846.5(3) A3, Z=4; C25.5H39BrClN5O8.5Re (3BrClxa0·xa01.5MeOHxa0·xa0H2O): triclinic P 1 , a=11.818(2) A, b=13.292(2) A, c=14.517(2) A, α=63.915(2)°, β=66.373(2)°, γ=67.416(2)°, V=1815.6(4) A3, Z=2.

Rhenium(I) carbonyl complexes of bis(N,N-diethylamino)carbeniumdithiocarboxylate, a novel inner-salt type sulfur donor ligand. Spectroscopic and structural studies

Abstract The reaction of the inner-salt SS donor ligand, bis( N , N -diethylamino)carbeniumdithiocarboxylate, Et 4 L, with [Re(CO) 5 Cl] afforded a red colored dinuclear rhenium(I) complex [Re 2 (CO) 6 (μ-Cl) 2 (μ-(Et 4 L)] in excellent yield, along with the mononuclear complex [Re(CO) 3 (Et 4 L)Cl]. The corresponding reactions of the ligand with [Re(CO) 5 Br] give only the mononuclear analogue, [Re(CO) 3 (Et 4 L)Br]. All the complexes were structurally characterized. The X-ray structure of the dinuclear complex revealed that two facially coordinated {Re(CO) 3 } + moieties are chelated by the novel inner-salt type sulfur donor ligand and are bridged by two chloride ligands. The Reue5f8CO bonds, trans to the S donors of the ligand are longer than the other Reue5f8CO bonds, evidently due to the strong trans influence of the ligand. IR and 1 H and 13 C NMR data indicate that all the complexes are substantially stable in solution. The dinuclear complex displays metal based and ligand based quasi-reversible oxidation and reduction couples, respectively, whereas the mononuclear complexes are unstable under the same electrochemical conditions.

Imaging of carbonic anhydrase IX with an 111In-labeled dual-motif inhibitor

We developed a new scaffold for radionuclide-based imaging and therapy of clear cell renal cell carcinoma (ccRCC) targeting carbonic anhydrase IX (CAIX). Compound XYIMSR-01, a DOTA-conjugated, bivalent, low-molecular-weight ligand, has two moieties that target two separate sites on CAIX, imparting high affinity. We synthesized [111In]XYIMSR-01 in 73.8–75.8% (n = 3) yield with specific radioactivities ranging from 118 – 1,021 GBq/μmol (3,200–27,600 Ci/mmol). Single photon emission computed tomography of [111In]XYIMSR-01 in immunocompromised mice bearing CAIX-expressing SK-RC-52 tumors revealed radiotracer uptake in tumor as early as 1 h post-injection. Biodistribution studies demonstrated 26% injected dose per gram of radioactivity within tumor at 1 h. Tumor-to-blood, muscle and kidney ratios were 178.1 ± 145.4, 68.4 ± 29.0 and 1.7 ± 1.2, respectively, at 24 h post-injection. Retention of radioactivity was exclusively observed in tumors by 48 h, the latest time point evaluated. The dual targeting strategy to engage CAIX enabled specific detection of ccRCC in this xenograft model, with pharmacokinetics surpassing those of previously described radionuclide-based probes against CAIX.

[ 64 Cu]XYIMSR-06: A dual-motif CAIX ligand for PET imaging of clear cell renal cell carcinoma

Carbonic anhydrase IX (CAIX) is a cell surface enzyme that is over-expressed in approximately 95% of cases of clear cell renal cell carcinoma (ccRCC), the most common renal cancer. We synthesized and performed in vitro and in vivo evaluation of a dual-motif ligand, [64Cu]XYIMSR-06, for imaging CAIX expression on ccRCC tumors using positron emission tomography (PET). [64Cu]XYIMSR-06 was generated in yields of 51.0 ± 4.5% (n=5) and specific activities of 4.1 – 8.9 GBq/μmol (110-240 Ci/mmol). Tumor was visualized on PET images by 1 h post-injection with high tumor-to-background levels (>100 tumor-to-blood and -muscle) achieved within 24 h. Biodistribution studies demonstrated a maximum tumor uptake of 19.3% injected dose per gram of radioactivity at 4 h. Tumor-to-blood, -muscle and -kidney ratios were 129.6 ± 18.8, 84.3 ± 21.0 and 2.1 ± 0.3, respectively, at 8 h post-injection. At 24 h a tumor-to-kidney ratio of 7.1 ± 2.5 was achieved. These results indicate pharmacokinetics superior to those of previously reported imaging agents binding to CAIX. [64Cu]XYIMSR-06 is a new low-molecular-weight PET ligand targeting CAIX, which can image localized and metastatic ccRCC.

111In- and IRDye800CW-Labeled PLA–PEG Nanoparticle for Imaging Prostate-Specific Membrane Antigen-Expressing Tissues

Targeted delivery of drug-encapsulated nanoparticles is a promising new approach to safe and effective therapeutics for cancer. Here we investigate the pharmacokinetics and biodistribution of a prostate-specific membrane antigen (PSMA)-targeted nanoparticle based on a poly(lactic acid)-polyethylene glycol copolymer by utilizing single photon emission computed tomography (SPECT) and fluorescence imaging of a low-molecular-weight, PSMA-targeting moiety attached to the surface and oriented toward the outside environment. Tissue biodistribution of the radioactive, PSMA-targeted nanoparticles in mice containing PSMA(+) PC3 PIP and PSMA(-) PC3 flu (control) tumors demonstrated similar accumulation compared to the untargeted particles within all tissues except for the tumor and liver by 96 h postinjection. For PSMA(+) PC3 PIP tumor, the targeted nanoparticle demonstrated retention of 6.58% injected dose (ID)/g at 48 h and remained nearly at that level out to 96 h, whereas the untargeted nanoparticle showed a 48 h retention of 8.17% ID/g followed by a significant clearance to 2.37% ID/g at 96 h (P < 0.02). On the other hand, for control tumor, both targeted and untargeted particles displayed similar 48 h retentions and rates of clearance over 96 h. Ex vivo microscopic analysis with near-infrared versions of the nanoparticles indicated retention within PSMA(+) tumor epithelial cells as well as tumor-associated macrophages for targeted particles and primarily macrophage-associated uptake for the untargeted particles. Retention in control tumor was primarily associated with tumor vasculature and macrophages. The data demonstrate the utility of radioimaging to assess nanoparticle biodistribution and suggest that active targeting has a modest positive effect on tumor localization of PSMA-targeted PLA-PEG nanoparticles that have been derivatized for imaging.

A metal-mediated dimerization of the ligand bis(N,N-diethylamino)carbeniumdithiocarboxylate.

The title compound, methylene bis[bis(N,N-diethylamino)carbeniumdithiocarboxylate] pentachlorooxorhenium, (C(21)H(42)N(4)S(4))[ReCl(5)O], is the result of an unusual dimerization of the ligand bis(N,N-diethylamino)carbeniumdithiocarboxylate [(Et(2)N)(2)C(2)S(2)] upon reaction with [ReOCl(3)(PPh(3))(2)] in chloroform under reflux conditions. The compound was obtained as a dicationic moiety, with the molecular [ReOCl(5)](2-) anion providing the charge compensation. The planes of the carbenium and thiocarboxylate moieties are nearly perpendicular to one another and the backbone C-C bond length in the N(2)CCS(2) group is the same as a normal C-C single-bond length.

Anthranilic acid analogues as diamagnetic CEST (diaCEST) MRI contrast agents that feature an IntraMolecular-bond Shifted HYdrogen (IM-SHY)

Diamagnetic chemical exchange saturation transfer (diaCEST) agents are a new class of imaging agents, which have unique magnetic resonance (MR) properties similar to agents used for optical imaging. Here we present a series of anthranilic acid analogs as examples of diaCEST agents that feature an exchangeable proton shifted downfield, namely, an intramolecular-bond shifted hydrogen (IM-SHY), which produces significant and tunable contrast at frequencies of 4.8-9.3 ppm from water. Five analogs of N-sulfonyl anthranilic acids are all highly soluble and produced similar CEST contrast at ~6-8 ppm. We also discovered that flufenamic acid, a commercial nonsteroidal anti-inflammatory drug, displayed CEST contrast at 4.8 ppm. For these N-H IM-SHY agents, the contrast produced was insensitive to pH, making them complementary to existing diaCEST probes. This initial IM-SHY library includes the largest reported shifts for N-H protons on small organic diaCEST agents, and should find use as multifrequency MR agents for in vivo applications.

Anthranilic acid analogs as diamagnetic CEST MRI contrast agents that feature an intramolecular-bond shifted hydrogen: NOVEL ANTHRANILIC ACID IM-SHY DIACEST MRI AGENTS

Diamagnetic chemical exchange saturation transfer (diaCEST) agents are a new class of imaging agents, which have unique magnetic resonance (MR) properties similar to agents used for optical imaging. Here we present a series of anthranilic acid analogs as examples of diaCEST agents that feature an exchangeable proton shifted downfield, namely, an intramolecular-bond shifted hydrogen (IM-SHY), which produces significant and tunable contrast at frequencies of 4.8-9.3 ppm from water. Five analogs of N-sulfonyl anthranilic acids are all highly soluble and produced similar CEST contrast at ~6-8 ppm. We also discovered that flufenamic acid, a commercial nonsteroidal anti-inflammatory drug, displayed CEST contrast at 4.8 ppm. For these N-H IM-SHY agents, the contrast produced was insensitive to pH, making them complementary to existing diaCEST probes. This initial IM-SHY library includes the largest reported shifts for N-H protons on small organic diaCEST agents, and should find use as multifrequency MR agents for in vivo applications.